You're being too generous. Calling typescript a rewrite shows the author chose something as an example they clearly don't understand the first thing about.
I'm not a fan of python so I was prepared to commiserate but...
Tuples, Sets, Dicts, Lists
These are all useful in every language... I don't use tuples that often, but lists/arrays and associative arrays/dictionaries/hashmaps are in every language and completely different from each other, and there are plenty of reasons to use sets when that is what your data actually is and you get easy access to set operations
For DS/2DS/3DS specifically, there is no emulation hardware that has resistive touchscreen, which I think is superior to capacitive for many games. For 3DS, the same thing applies to the 3D capabilities. Additionally, I'm under the impression that 3DS emulation isn't fully reliable for the full library, but I may be out of date.
TLDR; emulation may not be as feature complete or as quality as original hardware.
If we hadn't let them call it sideloading for so long it would be easier to have the conversation about the implications with less savvy people more easily.
You are correct that it is the deserializer's choice. You are incorrect when you imply that it is a good idea to rely on behavior that isn't enforced in the spec. A lot of people have been surprised when that assumption turns out to be wrong.
There are really good uses for XML. Mostly for making things similar to HTML. Like markup for Android UIs or XAML for WPF. For pretty much everything else the complexity only brings headaches
Information set isn't a description of XML documents, but a description of what you have that you can write to XML, or what you'd get when you parse XML.
This is the key part from the document you linked
The information set of an XML document is defined to be the one obtained by parsing it according to the rules of the specification whose version corresponds to that of the document.
This is also a great example of the complexity of the XML specifications. Most people do not fully understand them, which is a negative aspect for a tool.
As an aside, you can have an enforced order in XML, but you have to also use XSD so you can specify xsd:sequence, which adds complexity and precludes ordered arrays in arbitrary documents.
https://en.wikipedia.org/wiki/Service_mesh